Jason Gilbert Giambi (; born January 8, 1971) is an American former professional baseball first baseman and designated hitter. In his Major League Baseball (MLB) career, which began in 1995, Giambi played for the Oakland Athletics, New York Yankees, Colorado Rockies, and Cleveland Indians. He is the older brother of former MLB player Jeremy Giambi.
Giambi was the American League (AL) MVP in 2000 while with the Athletics, and is a five-time All-Star, who led the AL in walks four times; in on-base percentage three times; and in doubles and slugging percentage once each; he also won the Silver Slugger Award twice.
Giambi has publicly apologized for using performance-enhancing drugs during his career.